The Institute of Electrical and Electronic Engineers (IEEE) 802.11 wireless communication standard defines two main modes of operation: Infrastructure and ad-hoc. The infrastructure mode assumes that there is an Access Point (AP) which enables clients, also called stations (STA), to connect to a wired network. The ad-hoc mode, on the other hand, mainly concerns itself with wireless peer-to-peer connections among clients. In the infrastructure mode all clients connect to the AP and send their messages through it. In the ad-hoc mode the clients send messages directly to each other. There is a third Wireless Distribution System (WDS) communication scheme that enables APs to send wireless messages to each other.
According to the 802.11 standard, a client that needs to send data to an access point in the infrastructure mode first goes through authentication and association. A client that needs to send data to another client in the ad-hoc mode may go through authentication, but authentication is not required. The 802.11 standard does not specify the precise mechanism for establishing WDS connections. Once the infrastructure, ad-hoc or WDS connections are established, data messages, such as 802.11 frames, may be sent.
Table 1.0 and FIG. 1 show how the header in a 802.11 protocol frame 25 identifies the direction of frames 25. The mechanism consists of two bits: a “From DS bit” and a “To DS bit”. A Distribution System (DS) 23 can be any communication network used for transporting information to or from a client. For example, a Wide Area Network (WAN), Local Area Network (LAN), packet switched, circuit switched or any other type of wired or wireless network.
In FIG. 1, an access point 20 is connected to a wired LAN 21 that provides access to the DS 23. When the protocol frame 25 is sent from a client 18 to the AP 20 in the infrastructure mode 14, the To DS bit is set to 0 and the From DS bit is set to 1. When the AP 20 sends a frame 25 back to the client 18, the From DS bit is set to 0 and the To DS bit is set to 1. In the ad-hoc mode 12, when clients 18 send frames to each other, the From DS bit is set to 0 and the To DS bit is set to 0. In the WDS mode, the From DS bit is set to 1 and the To DS bit is set to 1.
This is documented in the IEEE 802.11 spec and shown in table 1.0 below.
TABLE 1.0ToFromDSDSAddress 1Address 2Address 3Address 4Meaning00DASABSSIDN/ASTA to STAdata frame01DABSSIDSAN/AData frameto DS10BSSIDSADAN/AData framefrom DS11RATADASAAP to APWDS data
The setting of the To DS and From DS bits also determine how addresses are used. The 802.11 frames sent between the client 18 and the AP 20 in the infrastructure mode use A3 (3 address) frames. The 802.11 frames sent between the client 18 and another client 18 in the ad-hoc mode are also A3 frames. The frames sent between one AP 20 and another AP 20 in the WDS are A4 (4 address) frames.
The contents of the address fields are determined by the direction of the sent frame 25. The DA is the destination address and the SA is the sender address. The BSSID is the Basic Service Set ID in the infrastructure mode. The BSSID is the Independent Basic Service Set ID (or IBSSID) in the ad-hoc mode. The RA is the receiver address and TA is the transmitter address.
In the A3 frame, the DA is equivalent to the RA and the SA is equivalent to the TA. This is because A3 frames are sent over a single hop link. The A4 frames are sent over multiple hops and the RA and TA change hop by hop where the DA and SA do not. Thus, the WDS connections support layer 2 forwarding.
The protocol message formats (headers and addressing) are important to the operation of the system as a whole because they are used by Media Access Control (MAC) firmware and software for filtering received messages. With broadcast media, the MAC layer determines which messages are processed and which are discarded. Thus, the header settings have to be set correctly in order to implement a meshing system architecture with existing hardware and firmware.
The infrastructure mode 14 and the ad-hoc mode 12 are mutually exclusive. A client 18 cannot operate in the infrastructure mode 14 and the ad-hoc mode 11 at the same time. Thus, client 18A operating in the infrastructure mode 14 cannot communicate with the client 18B or 18C operating in the ad-hoc mode 12. Similarly, clients 18B and 18C operating in the ad-hoc mode 12 cannot communicate to client 18A operating in the infrastructure mode 14 or the DS 23 via the AP 20.
This presents a problem for networks where messages need to be sent to any type of AP or client any time they are within range. The present invention addresses this and other problems associated with the prior art.